Tobacco smoke continues to be cited as the causative agent in a wide number of human diseases and pathologies. The dangers from tobacco smoke have been extended to include health problems derived from the passive inhalation of tobacco smoke byu non-smokers. This SBIR proposal addresses the need for a rapid, sensitive, and specific enzyme-linked immunosorbent assay for cotinine, the major metabolite of nicotine, which can be performed by physicians in the field. We propose to modify our current, commercially available ELISA for cotinine by developing a novel assay format so that the assay an be performed without instrumentation for a clear discrimination between non-smokers, non-smokers passively exposed to tobacco smoke, and active smokers. Our specific goals are to generate new enzyme-antibody conjugates and new antigen-enzyme conjugates and put them in an assay format which will generate a color in the presence of continue at levels of 5 to 500 ng/ml and remain colorless in the absence of cotinine.